The value here is not that they are easily solvable, with enough effort your could probably write something that solves these too. Thing is, are you willing to

The value here is not that they are easily solvable, with enough effort your could probably write something that solves these too. Thing is, are you willing to go through that effort for something that only a few sites use? This is in contrast to ReCaptcha, which is used my millions of sites, so using crowdsourcing and systems to make them easy to use is worth it there. For a long time I used the fixed captcha, "What is 1+1?", but written in my local language, and managed to filter out all the spam...